1. Field of the Invention
The present invention relates to a display controller for CRT and flat panel display apparatus, such as plasma display apparatuses.
2. Description of the Related Art
Along with the development of microcomputers, a variety of personal computers have been developed. Some microcomputers employ, flat panel display devices, such as plasma display apparatuses, as a display apparatus. The plasma display apparatus is controlled by a controller for a CRT display apparatus (to be referred to as a CRT controller hereinafter).
Meanwhile, a cathode ray tube (CRT) display apparatus is widely used as a display apparatus for personal computers. Therefore, a variety of application programs have been developed for CRT display apparatuses. A demand has arisen for effective use of the application programs, developed for CRT display apparatuses, in conjunction with the plasma display apparatuses. That is, a plasma display apparatus is used as a main display apparatus, and a CRT display apparatus is connected as an option, so that the two types of display apparatuses are selectively used in accordance with application programs. In this case, an error occurs when an application program for a CRT display apparatus executes a display command using a plasma display apparatus. This error results due to the fact that the CRT display apparatus can desirably change a dot size and the plasma display apparatus, however, has a fixed dot size. Therefore, when display is made in various display modes of different display resolutions, the CRT display apparatus can cope with this, but the plasma display apparatus cannot. For this reason, when a ratio of the number of dots in the vertical direction to that in the horizontal direction of a display screen of the CRT display apparatus is different from that of the plasma display apparatus, an actual image on the display screen of the plasma display apparatus is distorted, resulting in poor visual recognition property. In addition, a display font of the plasma display apparatus is also distorted, resulting in poorer visual recognition property.